This invention relates to friction welding and, more specifically, to friction welding of one or more metal structural members to form a tailored blank.
Structural devices are often formed as assemblies of a number of smaller structural members made of metal. Such assembling of individual members may be necessary to form devices that are too large or too complicated to be formed by conventional manufacturing methods. For example, such factors as casting sizes, forging sizes, available plate and block sizes, and the like can limit the size and geometry of the structural members that can be manufactured. To form larger or more complex devices, the structural members are typically assembled by joining the individual structural members using a variety of known joining techniques including, for example, mechanical fastening or welding.
Joints formed by mechanical fasteners such as rivets, screws, and bolts typically require an overlap of the structural materials at the joint. The fasteners and the overlap of material result in an increase in weight of the joint and the structural assembly. The joint can also introduce areas of increased stress, for example, around holes drilled for receiving rivets. Alternatively, weld joints can be formed to join the structural members, sometimes requiring little or no overlap of material. However, the formation of conventional weld joints, such as by arc or electron beam welding, can result in undesirable dimensional changes in the structural members. Welding can also introduce porosity or other discontinuities into the structural members or otherwise cause unwanted changes to the material properties of the structural members.
Friction welding has also been proposed as an alternative to conventional welding methods for joining members. Linear friction welding and rotational friction welding can be used to form strong joints without reducing the mechanical characteristics of the joined materials or causing significant dimensional changes. Conventional linear and rotational friction welding require one member to be moved, i.e. oscillated or rotated, and urged against the other member.
It is known to friction weld structural members together to make a tailored blank [which terms are used interchangeably herein] that is later machined. Typically the tailored blank approximates the desired dimensions and configuration of the final structural assembly and therefore requires little machining or other subsequent processing to form the final structural assembly. The finished structural assemblies can be used as structural components of a vehicle, such as an aircraft, an automobile, or a marine craft. For example, a multiplicity of the structural assemblies can be joined to form a wing, wing support structure, fuselage, and the like of an airplane. Alternatively, the structural assemblies can be used in buildings, machinery, and the like.
Many structural assemblies have structural elements that intersect at substantially right angles. For example, numerous aircraft parts have stiffeners between two flanges, each stiffener having respective ends that intersect the respective flanges at substantially right angles. Both the flanges and stiffeners can be friction welded to the substrate or base member, but typically not to each other. A wedge block can be placed between a flange and a stiffener and friction welded in place to connect them. Alternatively, hydropillar welding can be used to friction weld stiffeners and flanges at their interfaces. The latter process involves drilling a hole in the parts at their interface and then rotating a rod and forcing it into the hole. The taller the structural members being welded together, the greater the diameter of the hole needed for hydropillar welding. This results in higher costs for machining and material.
There is a need for improvements in the art of friction welding metal structural members together at substantially right angles in order to minimize costs.